Adhesively correctable transfer medium with delayed alteration resistance characteristics

Abstract

The present invention relates to an ink formulation which may be coated on a flexible substratum to produce a typewriter ribbon or the like, wherein impressions made from such a ribbon are capable of adhesive removal shortly after being created on all conventional typing bonds and papers, but which impressions exhibit delayed alteration resistance whereby any attempt at correcting or removing the indicia by pressure sensitive adhesive means or altering the indicia by erasing will leave an obvious and permanent indication that a removal was attempted.

What is claimed is: 
     
       1. In a typewriter ribbon having a thin flexible substratum and an image yielding transfer layer capable of producing indicia which, in connection with typing bond, are initially adhesively removable and exhibit a delayed alteration resistance, wherein the improvement comprises said transfer layer including a water soluble salt which reacts with paper, said water soluble salt being selected from the group consisting of cupric chloride, ammonium acetate, calcium thoicyanate, potassium acetate, barium chloride, potassium permanganate, lithium acetate, iodine trichloride and strontium hydroxide. 
     
     
       2. A typewriter ribbon as in claim 1, wherein the content of the water soluble salt is between 0.2 to 12% by weight of the total ink formulation. 
     
     
       3. In a typewriter ribbon having a thin flexible substratum and an image yielding transfer layer capable of producing indicia which, in combination with typing bond, are initially adhesively removable and exhibit a delayed alteration resistance, wherein the improvement comprises said transfer layer including an organic acid which reacts with paper, said organic acid being selected from a group consisting of bromo acetic acid, monochloro acetic acid, acetic acid, citric acid, tartaric acid and oxalic acid. 
     
     
       4. A typewriter ribbon as in claim 3, wherein the content of the organic acid is between 0.2 to 12% by weight of the total ink formulation.